There is a known heating roller in which a heating medium fluid is circulated inside a cylindrical member, so that a sheet-like heat-treatment target object in contact with an outer peripheral surface of the cylindrical member is heated to a predetermined temperature to dry (Patent Literature 1). The heating medium fluid is provided for the purpose of making the temperature of a surface of the cylindrical member uniform, which cylindrical member constitutes a main body of the heating roller. This heating medium fluid is caused to flow into the cylindrical member through a flow path, which is provided through a core cylinder located in a space formed inside the cylindrical member, and then to flow out of the cylindrical member after passing through another flow path between an inner peripheral wall of the cylindrical member and an outer peripheral wall of the core cylinder.
Further, there is another known heating roller for heating a web with use of heated water whose temperature is easily adjusted in a range of 90° C. to 100° C. by blowing vapor into the heated water standing inside a cylindrical member (Patent Literature 2). In the heating roller, the vapor is blown into the heated water standing inside the cylindrical member, through a vapor supply duct, a vapor distribution duct, and a plurality of vapor blowing ducts. The heated water increases in amount due to such blowing of vapor, and an amount of increased part of the heated water is caused to move through a drain hole and then ejected via an opening.